Reduce high limit of dwqe(4) receive ring by one.

To avoid confusion between the head and tail pointer, leave a gap
in dwqe(4) receive descriptors.  This prevents a situation when no
RX interrupts are received.

from gerhard@; OK kettenis@ dlg@

diff --git a/sys/dev/ic/dwqe.c b/sys/dev/ic/dwqe.c
index e515fd0..97f874d 100644 (file)
--- a/sys/dev/ic/dwqe.c
+++ b/sys/dev/ic/dwqe.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: dwqe.c,v 1.16 2023/12/28 14:30:28 uwe Exp $   */
+/*     $OpenBSD: dwqe.c,v 1.17 2024/03/04 23:50:20 bluhm Exp $ */
 /*
  * Copyright (c) 2008, 2019 Mark Kettenis <kettenis@openbsd.org>
  * Copyright (c) 2017, 2022 Patrick Wildt <patrick@blueri.se>
@@ -754,7 +754,7 @@ dwqe_up(struct dwqe_softc *sc)
                rxb->tb_m = NULL;
        }
 
-       if_rxr_init(&sc->sc_rx_ring, 2, DWQE_NRXDESC);
+       if_rxr_init(&sc->sc_rx_ring, 2, DWQE_NRXDESC - 1);
 
        dwqe_write(sc, GMAC_CHAN_RX_BASE_ADDR_HI(0), DWQE_DMA_DVA(sc->sc_rxring) >> 32);
        dwqe_write(sc, GMAC_CHAN_RX_BASE_ADDR(0), DWQE_DMA_DVA(sc->sc_rxring));